The U.S. study looked at 481 sexually active, straight women with an average age of 20 who weren't in a committed relationship, and asked why they faked it. Their top four answers:

• Altruistic deceit (making the guy feel better)

• Fear and insecurity (avoiding bad feelings about the experience)

• Elevated arousal (turning herself on)

• Sexual adjournment (getting sex over with)

The first two answers fit traditional thinking about a faked orgasm — that it's for the man, or a woman's emotional well-being — but the third shows a new self-determination by women in bed, says study co-author Erin Cooper.

One caveat: The study looked at young, single women, and earlier studies have found this group can't achieve orgasm as easily as women in serious relationships, Time notes.